Scaphander grandis ( Minichev, 1967 )

Scaphander grandis ( Minichev, 1967) View in CoL

( Figs 15 View Figure 15 , 24 View Figure 24 , 25 View Figure 25 ; Table 2)

Meloscaphander grandis Minichev, 1967: 130–134 View in CoL , figs 25–29; 1969: 43.

Scaphander grandis View in CoL — Chaban et al. 2019a: 385–397, figs 1–6; 2019b: 12.

Scaphander interruptus — Valdés and McLean 2015: (in part) 119–121, figs 2–5, 9, 10.

Taxonomic history: Minichev (1967) described the species under the genus Meloscaphander from three specimens collected by the Russian ship Vityaz off South Alaska. He remarked on the similarity of these specimens to the shell and anatomy of Scaphander , but assigned them to Meloscaphander based on their visible spire. This species was redescribed and analysed phylogenetically by Chaban et al. (2019a), resulting in its reassignment to the genus Scaphander . Examination of the shells of the specimens studied anatomically by Valdés and McLean (2015) in their redescription of S. interruptus revealed that these specimens instead belonged to S. grandis . The shells of S. interruptus are distinct, for example, by lacking a visible spire (see the Remarks in this sections for a discussion).

Type material: Meloscaphander grandis Minichev, 1967 — Northwestern Pacific : south of Alaska, Vityaz cruise 29, station 4158, 46°56’06”N, 143°58’54”W, 4665 m, holotype, ZISP 1/62440 , H = 33 mm, images seen ( Fig. 24A View Figure 24 ) GoogleMaps .

Other material examined: Kurile-Kamchatka Abyssal Plain: one spc., dissected, ZSM Mol 20210094, H = 25 mm; one spc., sequenced, ZSM Mol 20210053, H = 24 mm; one spc., dissected and sequenced, ZSM Mol 20150062, H = 29 mm; one spc., dissected and sequenced, ZSM Mol 20210096, H = 23 mm; one spc., dissected, ZSM Mol 20210095, H = 24 mm; one spc., dissected, ZSM Mol 20210097, H = 21 mm; one spc., ZSM Mol 20210098, H = 19 mm; two spcs, ZSM Mol 20150050, H = 20 mm; two spcs, ZSM Mol 20150051, H = 24–28 mm; three spcs, ZSM Mol 20150052, H = 20–25 mm; 17 spcs, ZSM Mol 20150053, H = 16–23 mm; three spcs, ZSM Mol 20150056, H = 18–19 mm; one spc., ZSM Mol 20150057, H = 27 mm; one spc., ZSM Mol 20150059, H = 21 mm; four spcs, ZSM Mol 20150063, H = 18–24 mm. USA: California, Santa Barbara County, 230 km west of Point Arguello, one sh. (broken), LACM 1995-21.9, H = 24.5 mm; one sh. (broken), LACM 1991-131.3, H = 25 mm; one sh. (broken), LACM 1993-74.1, H = 25 mm; one sh. (broken), LACM 1991- 130.2, H = 24 mm; one spc., dissected, LACM 1991-133.3, H = 29 mm; one sh. (broken), LACM 1993-21.10, H = 11 mm; off Oregon, Tufts Abyssal Plain, one sh., LACM 1972-262.7, H = 26.5 mm; one sh., LACM 1972-264.1, H = 29.5 mm; one sh., LACM 1972-265.9, H = 10 mm; two spcs, LACM 1972- 263.7, H = 25.5–28 mm; four spcs, one dissected, LACM 1972-261.9, H = 14.5–21 mm; one spc., LACM 1972-272.7, H = 12 mm; one spc., LACM 1972-270.8, H = 8 mm; one sh., LACM 1972-266.6, H = 13 mm.

Diagnosis: Shell ovoid, elongate. Spiral sculpture composed of rows of irregular sub-rectangular punctuations. Spire small, flat or slightly raised, partly separated from body whorl by a suture widening into a narrow groove along upper part of parietal wall. Outer lip rounded posteriorly, forming a shoulder level with or below apex. Parietal wall with thickened callus, smooth white. Rachidian teeth sub-rectangular, broad. Prostate oval to cylindrical, short, separated from penial chamber by long, thin prostatic duct. Penial papilla bulbous, covered with wrinkles.

Shell ( Fig. 24 View Figure 24 ): Maximum H observed = 33 mm. Shell ovoid, elongate. Aperture wide, nearly as long as shell, narrowing posteriorly. Spire small, flat or partly raised, made of three to four whorls. Suture partly separating spire from body whorl, widening in a narrow groove along uppermost part of parietal wall. Posterior edge of outer lip joining body whorl immediately below spire in acute-like shoulder. Parietal wall covered with thick, smooth white callus. Spiral sculpture composed of punctuated striations. Punctations irregularly shaped, sub-rectangular. Thin, translucent periostracum. Shell white.

Radula ( Fig. 25A–C View Figure 25 ): Radular formula 22 × 1.1.1 (H = 28 mm). Lateral teeth curved, with weak denticulation on inner edge. Rachidian teeth sub-rectangular, broad, with upper cusps curved inwards.

Digestive tract ( Fig. 25D, E View Figure 25 ): Salivary glands medium long; surface uneven. Paired gizzard plates irregularly ovoid to sub-quadrate.

Male reproductive system ( Fig. 25F, G View Figure 25 ): Penial chamber cylindrical, lined with soft longitudinal ridges. Muscular penial papilla, bulbous, covered in wrinkles. Penial chamber separated from prostate by long, thin prostatic duct. Prostate cylindrical to oval, rounded at end.

Ecology: Found between 3585 and 5427 m depth. Feeds on foraminifera, diatoms, and small bivalves and gastropods ( Chaban et al. 2019a; present study).

Distribution ( Fig. 15 View Figure 15 ): Northern Pacific; Northeastern Pacific Abyssal Plain, south of Alaska ( Minichev 1967, Chaban et al. 2019a) down to offshore Santa Barbara, California (present study), to Northwestern Pacific Abyssal Plain along the Kurile-Kamchatka Trench ( Chaban et al. 2019a, 2019b; present study).

Remarks: This species is distinguishable from most other Scaphander species by its visible spire and the presence of a shoulder in the posterior edge of the outer lip of the shell. Scaphander tortuosus nom. nov. [= Scaphander sibogae ( Schepman, 1913) ] and Scaphander planeticus Dall, 1908 are the only other known Scaphander representatives with a distinct shell shoulder, but both species present enough conchological differences from S. grandis to be kept separate, because they are both significantly more ovate and less elongate than S. grandis .

Valdés and McLean (2015) considered S. interruptus to be the only species of Scaphander present in the Eastern Pacific and described its anatomy. In this study, we examined the material listed in their article and noticed the presence of a spire in the shell of the specimens used for the anatomical dissections, which S. interruptus lacks. After comparison of these shells with the type material for S. grandis and further anatomical observations, we concluded that the specimens dissected by Valdés and McLean (2015) are conspecific with S. grandis .